Exposure to Salmonella is frequent but requires a high dose of 1 to
100 million (eg improperly refrigerated foods; low dose for immunocompromised,
very young and the elderly or with decreased gastric acidity

Disease is due to microbial growth in body tisssue & not by ingestion of
foods contaminated with toxins as a result of microbial growth

Asymptomatic carriage-- Establishes in gall bladder (ressists bile
& bile salts); continuous feedback into intestine; known as carrier
state (2-5% typhoid patients become carriers & excrete 1 to 1000
million S. typhi /gm feces & also in urine); Carrier state is important
in transmission of the disease. Mary Mallon (1901), aka Typhoid Mary,
was the first carrier case to be detected; In 15 years infected 200 &
jailed to prevent spred of typhoid fever. Disease has declined due to
curative & preventative measures (heat killed injectable vaccines or
the new live oral vacciine; same efficacy but later has less side effects

Multiplies in intestinal epithelial cells (but not
invasive to other tissues) & produces an enterotoxin
(binds irreversibly to epithelial cells stimulating the
production of cyclic which changes cell permeability
leading to the secretion of water & electrolytes into the lumen.
12 to 20 litres of water lost-- dehydration; replacement of
electrolytes & water necessary is the best treatment;
Tetracycline decreases disease period; vaccines provide
short immunity but natural infections provide a longer
duration (against enterotoxin & cells)

Culture in alkaline medium (high pH decreases the growth
of other bacteria)

Vibrio parahemolyticus

Habitat is salt water and requires &gt 2% NaCl for growth
in laboratory media (halophilic) Gastroenteritis from
contaminated shell fish, crabs; USA, Japan, Hawaii Large
nos. within 24 hr & recovery follows in a few days.